This invention relates to an electronically controlled distributor type fuel injection pump adapted for use in internal combustion engines, particularly in diesel engines.
Among conventional distributor type fuel injection pumps, an electronically controlled type is known, e.g. from Japanese Provisional Patent Publication No. 57-91366, wherein the fuel injection quantity and injection timing of the fuel injection pump is electrically controlled. According to this proposed type, a governor, an injection timing control device and a control sleeve are omitted from the fuel injection pump, but a single solenoid valve is employed instead for controlling the fuel injection quantity and the injection timing through its opening and closing actions, in such a manner that the fuel injection is initiated upon opening of the solenoid valve and terminated upon closing of the same valve. Therefore, the solenoid valve is required to have high responsiveness enough to achieve precise control of the fuel injection quantity and the injection timing. To this end, the solenoid valve should be capable of producing a large electromagnetic force. However, to produce such a large electromagnetic force, the solenoid valve inevitably has to be large in size, resulting in increased manufacturing cost as well as increased electric power consumption. Besides, the solenoid valve of the proposed type is constructed and arranged such that pressurized fuel acts upon the valve body in a direction of opening same, requiring a still larger electromagnetic force sufficient to overcome the pressure of the pressurized fuel so as to hold the valve body in its closed position. This also necessitates designing the solenoid valve to be large in size, further increasing the manufacturing cost as well as the electric power consumption.